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Total laryngectomy is a surgical procedure that involves removal of the entire larynx or voice box to treat cancer. After the removal of the larynx, a stoma is placed to allow the patient to breathe; however, the loss of their voice box renders them unable to speak normally. Even with the help of speech therapists, the patient’s voice will no longer be human-like. But the researchers at Western Sydney University developed a noninvasive prosthetic that replicates a human-sounding voice.
Laryngectomy and Stoma
Laryngectomy is a procedure often used to treat cancer of the larynx, severe injury to the neck or radiation necrosis. Removal of a part or the entire larynx depends on the condition. After the procedure, the connection between the esophagus and the trachea will no longer be available. While breathing can be done through a surgical hole in the neck called stoma, the patient must learn to swallow in a new way. But for a week or so, healthcare providers will feed the patient through a dedicated tube.
A stoma is a substitute for the normal breathing pathway modified during surgery. The breathing stoma is permanent and must be cleaned and moistened to avoid problems. Unlike with air coming through the nose, the air from a stoma is drier and colder, and may even contain dust particles that can irritate the lungs. When the dry, cold air reaches the airways, mucus is produced and can accumulate around the stoma. So it is the patient’s duty to protect the breathing stoma from extreme temperatures, fumes, smoke, and dust, and clean it to prevent mucus from building up.
Researchers at the MARCS for Institute for Brain, Behavior, and Development at Western Sydney University developed a bionic voice to aid people who had their larynx medically removed due to cancer. The device is an electronic prosthetic that produces high-quality sound without any input from the nerves of the larynx; instead, it uses the respiratory system to generate a voice that sounds human-like.
“Think of a bionic arm – which is a prosthetic, controlled by signals that are sent from the brain to a missing limb. A bionic voice is the same concept. It is effectively a prosthesis that restores speech to laryngectomy and tracheostomy patients and is able to be controlled naturally by messages sent from the brain to the missing larynx,” said Dr. Farzaneh Ahmadi, a postdoctoral research associate.
Typically, people who had their larynx removed use an electronic larynx to communicate verbally. It has the size similar to a small electric razor, powered by batteries, which produces a strong sound. The sound is produced by the vibrations generated by the device when placed under the chin or on the cheek. The device makes the buzzing vibration that reaches the throat and mouth of the patient. The electronic larynx allows the patient to immediately regain their voice and does not require too much maintenance. But the drawback of the device is that it produces a mechanical voice.
Some prosthetic devices available for laryngectomy have been found to have significant limitations. These devices require surgical applications to the stoma that translates to an invasive procedure, a chance of infections, and possible health complications. Moreover, the result usually ends up with a voice that is hoarse and whispery.
Another device called the pneumatic artificial larynx is an option to help the person speak. PAL uses the air to produce a humming sound and the movements of the lips, tongue, and velum convert the sound into speech. PAL is outdated due to being cumbersome and unhygienic, but the researchers discovered something essential with the old technology.
“With a pneumatic device – like the PAL – it is possible to recreate the function of the larynx and generate a voice using only respiration and without any nerve input. This means, no surgery would be required; the device would be completely non-invasive, and there is also the potential for the voice to be more human-like and better quality,” said Dr. Ahmadi.
When a healthy person speaks, the vocal folds produce the sound that is called a “voice.” The voice reshapes if the person moves their face, tongue, and lips. A person who had laryngectomy can still use their face, tongue, and lips, and only lack the vocal folds. The bionic voice mimics the missing vocal folds in people who lost their larynx and uses respiration to produce clear, high-quality and intelligible voice without relying on any input by the nerves or muscles of the larynx. The pre-clinical trial of Pneumatic Bionic Voice has matched the 98.4 percent accuracy of the PAL.
“We will effectively be providing patients with an artificial larynx that can be controlled automatically at any speech rate – able to stop and start, speed up and slow down, with clear diction and pitch,” says Dr. Ahmadi.
The team behind the bionic voice is now partnering with another research team at the University of Nagoya in Japan. The next study is to match the naturalness found in PAL.
[메디컬리포트=Ralph Chen 기자]